His announcement comes within days of being cleared by the Harris County District Attorney's Office of accusations he misused the port's boat for a dinner cruise and then altered records to conceal the event. Dreyer had invited prosecutors to investigate in May in an effort to clear his name.

"The frustrating part of it is - and maybe I was a little naive on this, I don't know - I can see what needs to be done, but I can't get those things done because of the politics," Dreyer said after the port commission's monthly meeting Tuesday. "I wanted to apply some business techniques, some things I've done in the past and been successful at. We've done a lot of that, but fighting the constant battle of politics … is just not something I want to do."

For example, he said, the port implemented a hiring freeze last year in consideration of the struggles of other local governments. Dreyer had sought to hire more staff to accommodate the port's growth.

The politics got harder last spring, when a storm of media allegations engulfed Dreyer and port Chairman Jim Edmonds.

Members of the Harris County Commissioners Court - which appoints two of seven port commissioners - questioned Dreyer's boat tour and Edmonds' former consulting job with a company that does business with the port.

The County Attorney's Office investigated the port and issued a report in September criticizing its secretive culture. The state Sunset Commission soon will undertake a review of the agency's operations.

"You go home and see yourself on TV," Dreyer said. "Come on, nobody wants to see that."

'Very talented, capable'

Port Commissioner Elyse Lanier, a frequent Dreyer critic, said she does not fault him, given his corporate background, for not anticipating the public nature of the role.

"When you're in the private sector, you do things differently," Lanier said. "(Here) it's not just politics. You have seven commissioners that want to be involved. We're here to set policy and I think our opinions have to be considered. There was a point at which that didn't happen."

Of Dreyer's departure, Lanier said, "It's probably good for him, it's probably good for us."

Edmonds also expressed surprise at Dreyer's announcement, calling him "a very talented, capable man." He said he would make a recommendation to the commission in the coming weeks on the hiring of a firm to search for a replacement.

Dreyer, whose contract ends in September, said he will serve until a replacement is named.

"He really embraced how the port can continue to grow and develop, with the Panama Canal opening up in three years," Moseley said. "I'm hopeful that momentum is still in place with the next executive director, because it's the right vision for Houston."

County Judge Ed Emmett said that if he had been in Dreyer's position, he might have made the same decision.

"He was trying to bring businesslike changes to the port, and when he terminated Argentina James, it appears the port commissioners chose sides and he got caught in the middle," Emmett said.

James, the port's former vice president of public affairs, was granted a severance deal that will see her collect $380,000 in monthly installments for consulting work.

Precinct 2 Commissioner Jack Morman, who asked the county attorney to investigate the port's operations, was cautious in assessing Dreyer's move.

"I feel like this could, potentially, be a good thing, but it's got to be bigger than just one person," Morman said. "It's the culture out there."

Dreyer said he has worked to change the port's practices. Before he arrived, Dreyer said, the agency did not make basic business calculations when considering projects, pointing to the $108.4 million Bayport Cruise Terminal - which has failed to attract a regular cruise ship since it opened in 2009 - as a consequence of such "decision-making by intuition."

Controls instituted

The commission now approves an annual budget, has a strategic plan, reviews monthly financial reports, is drafting a whistle-blower policy and discusses policy through several task forces, things Dreyer said did not happen before he was hired.

On Friday, Bill Moore, chief of the public integrity division in the District Attorney's Office, issued a letter clearing Dreyer of wrongdoing for his April 2009 use of the port's boat for a dinner event. The event was in keeping with port policies, Moore wrote, adding that the allegations that Dreyer had tampered with government records were false.